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TT: Fachverband Tiefe Temperaturen
TT 35: Correlated Electrons: Quantum-Critical Phenomena - Experiment I
TT 35.3: Vortrag
Dienstag, 1. April 2014, 10:00–10:15, HSZ 204
The Spin-1/2 XXZ Chain System Cs2CoCl4 in a Transverse Magnetic Field — •Oliver Breunig1, Markus Garst2, Eran Sela2,3, Benjamin Buldmann2, Petra Becker4, Ralf Müller1, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln — 2Institut für Theoretische Physik, Universität zu Köln — 3Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University — 4Institut für Kristallographie, Universität zu Köln
Cs2CoCl4 consists of CoCl4 tetrahedra that form chains along the crystallographic b axis. Due to a strong single-ion anisotropy the Co2+ orbital S=3/2 ground state is split into two Kramers doublets. Thus, at low temperatures a description of the lower doublet in terms of an effective spin-1/2 with an additional easy-plane anisotropy arises. By comparing measurements of specific heat and thermal expansion to exact finite-size diagonalization, we show that Cs2CoCl4 at temperatures below 2 K realizes the spin-1/2 XXZ chain in a transverse field [1]. Our data indicate a quantum phase transition at a critical field of ∼ 2 T before around 3.5 T the description in terms of an effective spin-1/2 chain becomes inapplicable. Considering both thermal as well as virtual excitations of higher crystal field states, we find that the spin chain is in the XY-limit with an anisotropy Jz/J⊥≈ 0.12 substantially smaller than previously believed. This work has been supported by the Deutsche Forschungsgemeinschaft via SFB 608 and FOR 960.
O. Breunig et al., PRL 111, 187202 (2013)